file 

Creates a table from a file. This table function is similar to url and hdfs ones.

file function can be used in SELECT and INSERT queries on data in File tables.

Syntax

file(path, format, structure)

Parameters

  • path — The relative path to the file from user_files_path. Path to file support following globs in read-only mode: *, ?, {abc,def} and {N..M} where N, M — numbers, 'abc', 'def' — strings.
  • format — The format of the file.
  • structure — Structure of the table. Format: 'column1_name column1_type, column2_name column2_type, ...'.

Returned value

A table with the specified structure for reading or writing data in the specified file.

Examples

Setting user_files_path and the contents of the file test.csv:

$ grep user_files_path /etc/clickhouse-server/config.xml
    <user_files_path>/var/lib/clickhouse/user_files/</user_files_path>

$ cat /var/lib/clickhouse/user_files/test.csv
    1,2,3
    3,2,1
    78,43,45

Getting data from a table in test.csv and selecting the first two rows from it:

SELECT * FROM file('test.csv', 'CSV', 'column1 UInt32, column2 UInt32, column3 UInt32') LIMIT 2;
┌─column1─┬─column2─┬─column3─┐
│       1 │       2 │       3 │
│       3 │       2 │       1 │
└─────────┴─────────┴─────────┘

Getting the first 10 lines of a table that contains 3 columns of UInt32 type from a CSV file:

SELECT * FROM file('test.csv', 'CSV', 'column1 UInt32, column2 UInt32, column3 UInt32') LIMIT 10;

Inserting data from a file into a table:

INSERT INTO FUNCTION file('test.csv', 'CSV', 'column1 UInt32, column2 UInt32, column3 UInt32') VALUES (1, 2, 3), (3, 2, 1);
SELECT * FROM file('test.csv', 'CSV', 'column1 UInt32, column2 UInt32, column3 UInt32');
┌─column1─┬─column2─┬─column3─┐
│       1 │       2 │       3 │
│       3 │       2 │       1 │
└─────────┴─────────┴─────────┘

Globs in Path 

Multiple path components can have globs. For being processed file must exist and match to the whole path pattern (not only suffix or prefix).

  • * — Substitutes any number of any characters except / including empty string.
  • ? — Substitutes any single character.
  • {some_string,another_string,yet_another_one} — Substitutes any of strings 'some_string', 'another_string', 'yet_another_one'.
  • {N..M} — Substitutes any number in range from N to M including both borders.

Constructions with {} are similar to the remote table function.

Example

Suppose we have several files with the following relative paths:

  • 'some_dir/some_file_1'
  • 'some_dir/some_file_2'
  • 'some_dir/some_file_3'
  • 'another_dir/some_file_1'
  • 'another_dir/some_file_2'
  • 'another_dir/some_file_3'

Query the number of rows in these files:

SELECT count(*) FROM file('{some,another}_dir/some_file_{1..3}', 'TSV', 'name String, value UInt32');

Query the number of rows in all files of these two directories:

SELECT count(*) FROM file('{some,another}_dir/*', 'TSV', 'name String, value UInt32');

Example

Query the data from files named file000, file001, … , file999:

SELECT count(*) FROM file('big_dir/file{0..9}{0..9}{0..9}', 'CSV', 'name String, value UInt32');

Virtual Columns 

  • _path — Path to the file.
  • _file — Name of the file.

See Also

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